ProjectThe non-lethal effects of cougar (Puma concolor) predation on bighorn sheep (Ovis canadensis)
Predation is a trophic interaction that has direct effects on populations through prey mortality, but it can also lead to indirect effects, also called non-lethal effects, through predator-induced stress. These effects can be caused by hormonal changes or due to trade-offs with anti-predator tactics. Although these non-lethal effects of predation on the prey’s population dynamics have been documented experimentally, few studies, have quantified them in nature. My objectives, in the context of my MSc, are to evaluate if predation by a cougar (Puma concolor) can affect, through non-lethal effects, a wild population of bighorn sheep (Ovis canadensis) in Ram Mountain, Alberta, Canada. This population has been subject to two events of intense predation by a cougar, the first being between 1998 and 2002; and the second in 2013. My project can be separated in three parts. The first is to evaluate if this predation can affect lamb’s survival at three different stages, hence a combination of direct and indirect effects. The second part consists in the evaluation of potential strict indirect effects, that is the effect of cougar predation on females’ probability of gestation, female summer mass gain and lamb mass at weaning. The third part concerns the mechanisms behind the non-lethal effects. In other words, this last part is to investigate if the cougar predation has led to measurable anti-predator tactics through space use and group size. To conclude, my study can be a prime example of the quantitative measuring of the non-lethal effects of predation, the mechanisms behind them, and how importantly it can affect a wild prey population dynamics.